There are actually 2 maps. 1 is Desert Duel from Metal Gear Arcade and MGS4's story mode. The other is a modified version of Icebound Inferno. The only modification is to remove the blizzard.
OFW players will have to re-install MGO2 from step 1 again with a different backup that has a version of the game data with the new map and Icebound Inferno's changes.
CFW players don't have to do anything. The launcher will auto update it.